Vehicle lift racks have been around for quite some time, and are extremely useful in connection with performing services on vehicles of all types. In performing such services, the rack is designed to elevate the vehicle to a convenient heighth so that service personnel can comfortably perform wheel alignment operations, brakes and wheel bearing inspection and adjustment, and certain operations with respect to lubrication. In connection with wheel alignment services, the prior art has disclosed a form of rack in which the runways can be positioned in a slanted attitude to facilitate vehicle run-on and run-off, and it can be elevated to a normal horizontal position which is required in order to accomplish accurate wheel alignment measurements and adjustments.
Prior art vehicle lift racks are exemplified by the disclosures in MacMillan U.S. Pat. No. 3,088,547 of May 7, 1963, Lill U.S. Pat. No. 3,190,395 of June 22, 1965, and its reissue patent Re 26,232, Hunter U.S. Pat. No. 3,216,530 of Nov. 9, 1965, and Lill U.S. Pat. No. 3,252,544 of May 24, 1966. Each of these prior art patents embodies a vehicle rack in which runways are movable between slanted positions and horizontal positions by means of mechanism for lifting the run-on end portions of the runways into a horizontal position substantially level with the support for the front wheels of the vehicle. The lifting mechanisms have taken a number of different forms in which piston and cylinder lifting devices have played a prominent roll. Some of the piston cylinder devices have been applied directly to the runways, while other arrangements have utilized mechanical arrangements with the runways. The prior art has disclosed operating mechanisms of a rather complicated nature requiring great care in the initial installation, and continuing vigilance during the life of the apparatus to assure its proper functioning.